How do you start a war between vampires and werewolves? If you're the Devil, you bring in a temptress. And what begins as a quiet episode about friendship and betrayal turns into bloody chaos.

What's been interesting about this final series of Being Human is that it feels less like a continuation of the previous story lines than a miniseries that happens to be set in the same universe. And it seems to have given the writers an opportunity to refine some of the show's longstanding ideas. Last episode, we saw a real return to the notion of ghosts, vampires, and werewolves genuinely trying to be human, and this episode, along with an advancement of the plot, we saw a few other details polished up.

Most important is the notion, which has existed since the very beginning of Being Human, that vampires don't need human blood for survival, but are instead addicted to it. Granted, I haven't gone back and watched the old Mitchell episodes in a while, but Hal feels more like a junkie to me. We've seen his self-enforced zen crumble, and now he's exhibiting the behavior of an addict: becoming secretive, failing to notice the big bad things around him in his single-minded obsession, risking his relationships with his friends, and blaming others for his regression.

On Alex's end, there's a really lovely bit about her relationship to her eternal clothes. The fact that ghosts are stuck in the clothes that they died in has always been a significant detail, but there's an ocean of difference between Annie trapped in her comfy cozies because she happened to die at home and Alex in her date clothes. Alex has been complaining about her clothes all series, moaning and groaning that they're far girlier than her usual raiments. But in this episode, we get a deeper reason for her discomfort: She wore them to impress Hal, and now she lives with Hal, stuck with this permanent reminder that she found him worth impressing. It's a nice use of Being Human's supernatural rules to emphasize an emotional situation.

Then there's Tom, who gives us a completely different perspective on lycanthropy than George did. He's never seemed distraught about being a werewolf per se, but he's concerned about his ability to integrate with human society and live a happy, successful life. And now that he has his assistant manager job, he has his eye on a girl.

I was disappointed that, after last episode, Mr. Rook didn't realize that Captain Hatch was something more nefarious than he claims to be. But, like Hal, he seems to be focused on his own obsessions to the exclusion of seeing real evil. So he taps Natasha, a girl he once rescued from a vampires nest, to stir up trouble between Hal and Tom. Natasha courts Tom while encouraging Hal to feed from her.

It's almost Biblical, sending a temptress in to wreck the tenuous Eden of the roommates. But Natasha proves a reluctant serpent, endeared by Tom's awkwardness and seeing Hal as weak, but not evil. She's the one who finally confronts Rook and forces him to admit the truth to himself: That he hasn't had the powder keg explosion he hoped for because the Trinity has always been around to keep a lid on things. With the Trinity in place, he's out of job, unfunded and useless. The Devil has inspired a specific kind of evil, not one that causes good men to do nothing, but one that focuses the efforts of good men in the wrong direction. There are so many types of government agent that Rook could be a metaphor for.

And Hatch's scheme works. He uses his psychic influence to march Natasha into the roommates' house, where a freshly contrite Hal has allowed Alex to tie him up and break him of his blood lust once again. Natasha cuts him free before slicing her own throat. When Tom and Alex happen upon the scene, Tom believes at last that Hal is just like any other vampire, in need of destruction. After Alex kicks Hal out of the house, depriving Hal of his support network, Hal goes full vampire, relishing in the violence he has denied himself of for all these years.

But it's Alex, who has been so neglected by her roommates, who is literally invisible to Rook, who learns the truth about what Hatch is. Despite being discouraged by Hal, Alex has put on her Scooby cap all episode and investigated Hatch and the mysterious suicides. When she finally confronts him, Hatch, secure in his power, confesses that he is the Devil, and flings Alex back into her own grave. But now that Alex has discovered the true evil of the series, is it too late to draw her friends—and Rook—back from their personal demons and distractions?